Electrical heater element



"Jan; 11),1'928. "1,655,838

E. c. LACKLAND ELECTRICAL HEATER ELEMENT Filed May 7, 1924 -3 theseobjections and in additionwill be in- Patented J... 10, 1928.-

UNITED STATES 1,655,838 PAITEN-TOFFICE.

EDGAR C. LACKLAND, OF NEW HAVEN, CONNEGTICU'JL ASSIGNOR TO ROCKBESTOSPRODUCTS CORPORATION, OF

NEW HAVEN, CONNECTICUT.

Application filed Kay 7, 1924. Serial No. 711,568.

This invention relates generally to the construction of heater elementsfor use in-electrical heating devices.

In the manufacture of electrical heating 5 pads in the prior art it hasbeen the practice to wind a bare conductor on a flexible support ofinsulating material and to arrange the element thus produced in aconvoluted formation in order to obtain the necessary length ofresistance wire in a given space,

and then to enclose the heater element between ads of material having asuitable insulating quality. It has been known also to wind theresistance wire together with a yarn formed of cotton or other suitablematerial and to place this element within the heating pad to be formed.It has been found that the heating element formed in the latter manneris open to' the objection that a sharp bend produced in the elementtends to force the resistance wire out of its protective position incontact with the yarn so that the wire is then exposed and does not moveback into its protective position when the bend is removed from theconductor. This gives rise to a possibility of short circuiting theconductor or of setting fire to the material forming the pad. In eithertype of con struction referred to the insulation is not satisfactory andleads to the making of an inferior product. v

It is an object of the present invention to provide a heater element forthegeneral urpose referred to which will be free rom expensiveto-manufacture and will rovide in other ways an article su erior to t earticle produced in prior met ods of manufacture.

The invention includes the production of\ a heater element which formseither the weft or the warp element of a loosely woven fabric, theheater element consisting of a resistancewire so wound or wrapped in aspecially formed asbestos roving that the I wire is permanently situatedat substantially the axial center of the insulating wind-' ing orcasingprovided. By this construction a heater element is formed in which no toamount of bending can force the wire from its protected position at thecenter of the insulatin casing. The other element of the weave, tjat is,the warp or weft yarn is formed by a yarn produced by twi stingas- Ibestos roving threads of thesametypeu'sed provided for the heaterelement but the use of resistance wire in the form of an element of thewoven fabric produces a relatively pliable structure which particularlyfacilitates the use of the heater element in heating pads such as areused for therapeutic purposes. The fabric formed in this manner ispreferably of an open mesh character which, as will be seen, adds to thepliability desired and also enhanced the insulating qualities of thestructure.

It is possible to produce a multiple heating effect by the use of tworesistance wires woven together in the fabric from the same shuttle.Preferably in such a case the two elements would be. colored differentlyso as J to distinguish them apart in the assembly of the device.

In the drawings, in which a preferred embodiment of the invention hasbeen selected'for illustration, I

Figure 1 is a view in a more or less diagrammatic form of a heaterelement made in accordance with the invention,

enlarged scale of Figure 2 is a view on ana resistance wire element usedin the production of the device shown in Figure 1.

Figure 3 is a view similar to Figure 1 showing a modified form of theinvention.

Referring to the drawings for a more detailed description of theinvention, Figure 1 shows an open mesh fabric formed with a weft thread10 consisting of a suitably insulated resistance wire and of a series ofwarp threads 11 formed of insulating material similar'to andsubstantially the same sizeas is provided by the weft "thread ele- 'ment10. It will be noted that the fabric thus formed is of an open meshcharacter wound on areinforcing or carrier thread 14 and then'woundln-relatively close c011s on I the wire 12. By this structuralarrangement a yarn is formed having excellent heating and electricalinsulating qualities of asbestos fibers and with the tensilestrengthprovided by'the 'reinforcing thread which makes it trude orbreak throughthe insulation when thefabric is sharply bent.

' to form ayarn. In a preferred construction Thwarp threads 11' of thestructure are preferably formed of yarn members formed .of the samematerial'used in insulating the resistance wire. Preferably two threadreinforcing asbestos rovlngs are twisted together of the heater elementtwo rovings of this character are used in provldlng the lnsulatingwinding for the wire so that the warp elements and the weft element areof the same general character and diameter thereby forming a fabric of auniform character. It

' will be seen that the fabric thus formed has an open mesh formation,the effect of which is to produce a relatively spaced apart re-' lationbetween the stretches of the weft element 10 forming the heater element.In this I way a' doubly efiective insulation of the weftfelementstretches from each other is obtained. i

, In'a modified form of the invention shown in Figure 3 of the drawing adouble heater element 10 is provided formed of a pair of resistancewires wound as in Figure Q'and' woven into the fabric from the sameshuttle reel.

to permit of an identification in forming the connections to the sourceof current. This ing values since the separate resistance wiresPreferably the two elements are col-' 'ored differently'or otherwisedistinguished have different resistance capacities thereby providing acombination of three heat pro ducing values. 7

WhllG I have described my'invention with particular reference to aheating pad, ,itwill be readily understood that the same is not limitedthereto butmay be used in various other electrical heater devices inwhich the characteristics of the invention maybe useful, and thus whileI have described a preferred embodiment of my invention, it will "bereadily. understood that the same is not to be limited to all thedetails shown but is consisting-of thread reinforced asbestos rovingshelically wound about the wire, and the other elements comprise yarnsformed of asbestos rovings twisted together.

'2. A heating element for electrical heater devices comprising an openmesh woven fabric in which one element comprises a resistance wirehaving an insulating casing consisting of asbestos rovings helicallywound about the Wire, and the other elements comprise yarns formed ofthread reinforced asbestos rovings .twisted together.

3. A heating element for electricalheater devices comprising an openmesh woven fabno in which the weft element comprlses a resistance wirehavlng an insulatmg casing consisting of thread reinforced asbestosrovingsihelically wound about the wire, and the Warp elements compriseyarnsformed of thread reinforced asbestos rovings twisted 5 together.arrangement provides a combination of heat EDGAR o. LAGKLAND,

